KINNER and MAURER: POLYCHAETOUS ANNELIDS OF DELAWARE BAY 



also contained large rocks, small boulders, and 

 mussel beds. A detailed account of these areas can 

 be found in Maurer et al.^ Although Area I was 

 about 20 km off the Delaware Bay mouth, the 

 western portion of this area appeared to be 

 influenced by the hydrography of Delaware Bay. 

 Salinity ranged from 28.2 to 32.5%o and the sedi- 

 ment varied from silty-sand to gravelly sand. 

 However, a few sediment samples contained black 

 mud (30-33'^ silt-clay and 2.63-3.64% organiccon- 

 tent) (Watling et al. 1974). 



Offshore 



The oceanic or offshore area, termed midshelf 

 site (Figure 1, J), has been the subject of several 

 studies. An extensive review of the hydrography 

 and geology was presented by Bumpus et al.^" and 

 Milliman.ii Salinity was 31-40.0%o and the sedi- 

 ment was dominated by clean sand with some peb- 

 bles and dead shells at the collecting site. Ridge 

 and swale microtopography influences sediment 

 composition. Crests of the ridges contained clean 

 sand and swales or troughs consisted of shell and 

 flocculent material (Maurer et al. 1976). 



Results and Discussion 



A total of 125 species of poly chaetes, represent- 

 ing 34 families and 88 genera, were identified from 

 all the sampling areas. Eighty-three species and 

 25 families were collected within Delaware Bay 

 proper (Table 2, columns A-E). The Delaware Bay 

 samples usually showed less than 10 species and 

 250 individuals/m^. However, the most species 

 (95) were collected in the offshore samples. The 

 number of individuals per sample was much 

 higher at stations in the midshelf area. This was 

 also the only collection where the polychaetes 

 dominated the fauna. Infaunal samples in both the 

 bay and in the nearshore areas are otherwise 

 dominated by members of the Mollusca (Maurer et 

 al. see footnote 7; Watling et al. 1974). 



'Maurer, D., J. Tinsman, W. Leathern, and P. Kinner. 1974. 

 Baseline study of Sussex County, Delaware ocean outfalls. Rep. 

 Sussex County Engineer, Sussex County Delaware. Univ. Del., 

 Coll. Mar. Stud., 287 p. 



'"Bumpus, D. F., R. E. Lynde, and D. M. Shaw. 1973. Physical 

 oceanography. In S. B. Saila (editor). Coastal and offshore en- 

 vironmental inventory Cape Hatteras to Nantucket Shoals, 72 p. 

 Univ. R.I., Mar, Publ. Ser. 2. 



"Milliman, J. D. 1974. Marine geolog>-. /n S. B. Saila (editor). 

 Coastal and offshore environmental inventory Cape Hatteras to 

 Nantucket Shoals. Univ. R.I., Mar. Publ. Ser 3. 



Delaware Bay 



Intertidal — Cape Henlopen (E) 



Eight core samples (25 cm diameter x 25 cm 

 height) were taken each month for 25 mo on Cape 

 Henlopen near the mouth of the bay, from 1970 to 

 1972 (Figure 1). The study area was on the bay 

 side of the spit on a tidal flat with swash bars. 

 Eighteen species of polychaetes were collected in 

 the sampling area (Table 2, column E). The 

 number of species decreased gradually from fine to 

 coarse sand (Maurer unpubl. data). Large tube- 

 building polychaetes (Diopatra cuprea) and bur- 

 rowing infaunal species (Lumbrineris tenuis and 

 Scoloplos fragilis) occurred in highest densities in 

 the fine sand, whereas spionids and nephtyids 

 were better represented where sediment grain size 

 increased towards the ocean. Two species (S. 

 fragilis and Spio setosa) were particularly abun- 

 dant from the low to the high tide line. Scoloplos 

 fragilis was most common just above the reducing 

 layer in the sediment. Pista palmata was collected 

 only in the sand flat area. 



Baywide (A) 



The polychaete fauna in the upper bay (5-15%o) 

 was dominated by the deposit feeders Heteromas- 

 tus fUiformis and Scolecolepides viridis (Table 2, 

 column A). Glycera dibranchiata was also present 

 at a number of stations. Sediments in this area 

 ranged from M 4.2 to 7.9<^ (median grain size), 

 vdth generally poor sorting (o- = 2.4-3.90). At all 

 stations the numbers of individuals were very 

 small, with four individuals being the most re- 

 corded at one time. This paucity of individuals 

 was also evident in other groups of the benthic 

 fauna. 



Farther down the bay where salinities were 15- 

 25%o, there was an increase in number of species 

 and individuals. Thirty-two species were col- 

 lected, including all the six species recorded in the 

 area of 5-15%o (Table 1). The sediment showed a 

 much wider range of particle size (M 1.0-7.0</)) 

 than in the previous zone, with a tendency toward 

 better sorting in the larger sediment classes. 

 Heteromastus fUiformis was still the dominant 

 polychaete in fine sediments, with G. dibranchiata 

 important in coarser material. Deposit-feeding 

 polychaetes predominated, particularly on the 

 sides of the estuary in the finer sediment (Figure 

 2). The coarser sediments in the middle of the 



213 



